In this paper, we present a compact quantum model for both the electrostatic potential and electric charge in thin-film symmetric double-gate metal-oxide-semiconductor field-effect transistors with undoped body. As a novelty, both the resulting potential and charge have explicit expressions on bias and geometrical parameters. A comparison has been made between self-consistent numerical solutions of Schrodinger-Poisson equations and our model results with close agreement. Finally, the range of validity of the presented model is discussed. (C) 2010 Elsevier Ltd. All rights reserved.